I doubt there is any relay problem with the fan, but I do highly suspect (I think I'm right) that either the fan resistor or the blower fan are ruined.

That means a trip ALL the way inside the dashboard. Shops have no problem getting $400-500, and I've heard quotes of $700 or so for the job. Trust me, it is not exactly a delightful job to take on. This is a known weak spot in the 240 series.

If repaired properly the accident damage should not devalue the car's price, since many "accident free" cars are not accident free in the least. But they are called that. (Carfax is still missing some of these.) This way you know the story.

I would say that if you shop around, you can get someone to do the heater fan (that IS the problem, otherwise why would this person not have replaced a simple relay to sell the car with working heat?) for less than $500. Maybe a lot less. Around here you'd pay through the nose. If you do it yourself, it is an afternoon's work and $50 or so in parts (something to that effect). IT is NOT hard but it IS complex. Not a job for the mechanically disinclined.
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Chris Herbst, near Chicago.